Aperture blades schneider componon-s 50mm f2.8

[ericdan]

The Schneider componon-s 50mm f2.8 is supposed to be one of the better enlarger lenses. I noticed it only has 5 aperture blades which make the opening not very smooth. I thought that higher grade lenses usually have more aperture blades. Is that not so?!

 

[Donald Qualls]

The shape of the aperture makes no difference whatever when your image is in perfect focus.

Where aperture shape becomes noticeable is when the image is out of focus -- but under the enlarger, you generally want your projection to be perfectly focused.

For that matter, I have an Olympus Pen EES-2 with a square aperture at all openings (and artifact of the way the auto exposure works); I've never found anything objectionable about even the out-of-focus characteristics (though I don't do much night shooting with it, where light sources might show the aperture shape when out of focus).

 

[DREW WILEY]

The Componon S is a somewhat older lens that does a decent job - better in certain respects than the previous chrome Componons, but not quite in the same league as newer enlarging lenses. Unless you're adapting a lens like this for camera use, the specific number of blades is irrelevant.

 

[ic-racer]

Here are the MTF curves for 2.8 (wide open, smooth circle), 5.6 and 8. As you can see there is a dramatic improvement at f8 over f2.8, in spite of your worries. BTW where did you read that about he number of blades, I never heard of that in all the Schneider or Zeiss literature on pictorial lenses. In fact one of my favorite Zeiss lenses has only three blades and my coveted EE Switar which has only two!

 

[ic-racer]

Maybe you are confusing something with making or photoengraving using a screen. In that case the aperture shape 'shows through' to the dots.

 

[DREW WILEY]

I doubt he's even aware of process lenses, since he's speaking of 50mm focal length. Many process lenses had both multi-bladed apertures as well as a slot provision for diaphragm inserts. One version of Apo Nikkors had not only both of those, but an additional aperture with four blades designed to facilitate perfectly square rather than round dot reproduction. But multi bladed taking lens apertures were once routine, right up till the Copal 3S shutter. And now more blades are becoming favorable on even numerous 35mm camera lenses for sake of improved bokeh, depending on optical variables too. But when enlarging, something is awfully wrong if you have any depth of field issue; you only want one precise flat plane.

 

[MattKing]

The Schneider componon-s 50mm f2.8 is supposed to be one of the better enlarger lenses. I noticed it only has 5 aperture blades which make the opening not very smooth. I thought that higher grade lenses usually have more aperture blades. Is that not so?!

This reflects a very common, but incorrect photographic myth.
Even if true, it would have no relevance to enlarging lenses, because the number of aperture blades only affects the shape and appearance of out of focus areas, and who evaluates enlarging lenses based on their out of focus performance?
I expect the myth arose because in many cases, apertures with very few blades were used in very inexpensive cameras, most likely to keep costs low.

 

[DREW WILEY]

It had a lot to do with the size of the lens. It's difficult to pack a lot of blades in a small lens without them being fragile. I think the move to lesser blades was also about cost-efficiency in manufacture as well as improved durability through simplification. Some lenses potentially get shared in a multi-application sense. My Apo Nikkors are all multi-bladed and were cannibalized from a retired huge process camera, but perform better at enlarging than official enlarging lenses, and on a large format camera, are sharper than ordinary view camera lenses all the way from closeup to infinity. So multiple usage. But despite many blades, their bokeh is awful. And they were never made in anything shorter than 180mm, so wouldn't apply to this particular thread anyway. I'd have to look in my cabinet to see if I even still have my old 50mm Componon S. I rarely print 35mm film, and when I do, generally prefer a longer focal length lens, anywhere between 75mm and 105.

 

[ericdan]

Here are the MTF curves for 2.8 (wide open, smooth circle), 5.6 and 8. As you can see there is a dramatic improvement at f8 over f2.8, in spite of your worries. BTW where did you read that about he number of blades, I never heard of that in all the Schneider or Zeiss literature on pictorial lenses. In fact one of my favorite Zeiss lenses has only three blades and my coveted EE Switar which has only two!

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I didn’t read anything. I just looked at the lens as I changed the aperture.
No issues with the lens at all. I was just wondering since it looked so different from the Nikkor and Leitz 50mm enlarger lenses.